The Police Service of Northern Ireland has confirmed that a car bomb that partially exploded outside the province's policing board contained 400lbs of explosives. No one was injured in the blast, which also failed to damage the policing board's headquarters.

Matt Baggott, the PSNI Chief Constable, said the bombing and a gun attack against officers near the border were an attack on the entire community and would not succeed.

The violence over the weekend demonstrate that republican dissidents are widening their terror attacks across Northern Ireland, warned a policing board member.

Two men were arrested following a gun attack on officers in Co Fermanagh last night. Shot were fired at a police patrol in the border village of Garrison and PSNI officers returned fire. There were no reports of any injuries.

Dissident republicans were also blamed for a car bomb attack at the headquarters of the policing board. A car exploded outside the offices in Clarendon Dock yesterday evening. The vehicle had earlier been driven through a barrier by two men who then ran off. It is understood no one was injured in the incident. Both Garrison and the area around Clarendon Dock were cordoned off this morning.

SDLP policing board member Alex Attwood said the scale of dissident attack appears to be widening and organised after simultaneous incidents in Fermanagh and Belfast over the weekend.

The West Belfast assembly member said: "The incidents at Clarendon Dock and in Fermanagh are very grave concerns. It appears that the dissidents are broadening the scale of their attacks on democracy. The community must now broaden the scale of its response to the attacks and help the police with all information that may assist the prosecution of those responsible.

"The police, policing board and DPPs have been the most resilient institutions over the last decade. They have been tested time and time again. They have, and will, remain strong in their actions and resolve in the face of these latest developments."

There has been a marked upsurge in republican dissident terror attacks this year. On 7 March, the Real IRA killed sappers Mark Quinsey, 23, and Patrick Azimkar, 21, at Massereene Army base in Antrim.

Two days later the Continuity IRA shot PSNI Constable Stephen Paul Carroll in Craigavon, County Armagh.

Since the three murders the International Monitoring Commission has said there have been 11 attempts to kill members of the PSNI across Northern Ireland. The IMC – the body set up to monitor the activities of paramilitary groups – has also warned that the three main dissident groups, the Continuity IRA, the Real IRA and Oghlaigh na hEireann, are now working more closely together than in previous years.